Immunogenicity evaluation of next-generation vaccine platforms for prevention of Influenza and COVID-19

Background: Over the past hundred years, humans have experienced a long list of microbial threats to health. Among them, pandemics represent one of the major burdens for public health, economy and society. Influenza and most recently Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), being two pandemic-risk viruses both transmitted through the respiratory tracts, share many common features, and the constant emergence of new viral variants brings difficulties to permanently control the disease they cause [1]. Development of new, safer, cheaper, high-throughput vaccine platforms (such as DNA- or vector-based vaccines) targeting most conserved and immunodominant viral epitopes, might be the turning point to ensure control of infectious diseases and prevention of pandemics [2]. Aim: The aim of this thesis is to report immunogenicity findings of new vaccine platforms, which may contribute to their development as future vaccination strategies against pandemic-causing infectious diseases, such as Influenza and COVID-19. Methods: In Project 1, serum samples from BALB/c mice immunized intramuscularly with two different DNA-based Influenza vaccine constructs expressing the Influenza Neuraminidase (NA) protein have been tested in a pseudotype-based Enzyme-Linked Lectin Assay (pELLA) assay, in order to evaluate the presence of post-vaccination NA-inhibiting antibodies. In Project 2, we evaluated the potential of a Leishmania tarentolae (Lt)-purified SARS-CoV-2 recombinant RBD-SD1 antigen (“Lt-RBD”) and of a Lt-based vaccine platform expressing SARS-CoV-2 S protein (“Lt-spike”) combined with the Lt-RBD (LeCoVax-2) in inducing antigen-specific T cell mediated responses when administered to BALB/c mice via the mucosal (rectal, R) or systemic (subcutaneous, SC) route of immunization. Both Lt-RBD and LeCoVax-2 were used either adjuvanted or not. T cell responses (release of IFN-γ, IL-4, TNF-α) raised after vaccine administration were assessed by Enzyme-Linked ImmunoSpot (ELISpot) assay upon isolation of splenocytes. Results and Conclusions: Results from both Projects highlight an elicitation of immune responses after BALB/c mice immunization with either DNA-based or Lt-based vaccines. In Project 1, a positive titer of NA-inhibiting antibodies was especially detected in serum samples belonging to the mice group immunized with a high dose (10 μg) of the two different dbDNA™ vaccines, “Construct 1” and “Construct 2”, but an overall positive result was also detected in the group treated with a low dose (1μg) of “Construct 2”. These results support the use of the innovative dbDNATM as DNA-based vaccine platform for Influenza NA and the suitability of the pELLA assay for the immunogenicity assessment of this kind of NA-expressing vaccines. In Project 2, promising data have been obtained upon evaluation of antigen-specific cytokines-producing T-cell capacity of both the Lt-based platform LeCoVax-2 and the Lt-purified antigen RBD-SD1. When administered via the R route, the purified adjuvanted RBD-SD1 did not induce any detectable T-cell-mediated immune responses, in comparison with the relatively high production of Th1/Th2 cytokines observed after immunization with LeCoVax-2 (especially when adjuvanted). LeCoVax-2, however, was also effective when administered enterally without adjuvant. These results show immunogenicity of this innovative Lt-based platform also by mucosal immunization and pose the basis for further investigations. In conclusion, our results support further development of the two novel vaccine platforms evaluated. These studies are worthy to be conducted as they might give us a clue not only about the most immunogenic but also affordable and scalable vaccination strategy to use in order to promptly react to the next pandemic [4]

Influenza anti-stalk antibodies: Development of a new method for the evaluation of the immune responses to universal vaccine

Growing interest in universal influenza vaccines and novel administration routes has led to the development of alternative serological assays that are able to detect antibodies against conserved epitopes. We present a competitive ELISA method that is able to accurately determine the ratio of serum immunoglobulin G directed against the different domains of the hemagglutinin, the head and the stalk. Human serum samples were treated with two variants of the hemagglutinin protein from the A/California/7/2009 influenza virus. The signals detected were assigned to different groups of antibodies and presented as a ratio between head and stalk domains. A subset of selected sera was also tested by hemagglutination inhibition, single radial hemolysis, microneutralization, and enzyme-linked lectin assays. Pre-vaccination samples from adults showed a quite high presence of anti-stalk antibodies, and the results were substantially in line with those of the classical serological assays. By contrast, pre-vaccination samples from children did not present anti-stalk antibodies, and the majority of the anti-hemagglutinin antibodies that were detected after vaccination were directed against the head domain. The presented approach, when supported by further assays, can be used to assess the presence of specific anti-stalk antibodies and the potential boost of broadly protective antibodies, especially in the case of novel universal influenza vaccine approaches

The accuracy of burn depth diagnosis: Clinical assessment before and after enzymatic debridement

Abstract Introduction The most common technique used to determine burn depth is clinical assessment by experienced burn surgeons, although this has been shown to be reliable in only 60–75% of the cases. Overestimation of burn depth may result in needles surgery, while burn depth underestimation can led to an increased length of stay in the hospital, risk of contracture and hypertrophic scar formation. The aim of this study was to assess the clinical evaluation of burn depth before and after enzymatic debridement with Nexobrid®. Methods The study model was retrospective. 69 patient records were collected at our burn units, from Jan 2018 to Jan 2019. Each target wound was directly assessed by a single expert physician before and after enzymatic debridement. It was investigated whether the expert, by single wound, would have indicated the need for skin grafts before treatment with Nexobrid® and after treatment. Results Prior to treatment with Nexobrid®, the expert physician assessed that a graft was necessary for 47/69 patients (68.1%). Following debridement, the same expert deemed that the patients needing a graft were 19/69 (27.5%); analysing K-agreement, a 40.6% discrepancy between the pre and post-treatment opinion with Nexobrid® was observed. Discussion The use of Nexobrid® enzymatic debridement can positively affect burn depth clinical assessment, increasing its specificity and sensitivity, without any need for delay. This can lead to a significant change in clinical practice, minimizing the use of surgery, therefore increasing quality and precision of the reconstructive phase

Comparative analyses of SARS-CoV-2 binding (IgG, IgM, IgA) and neutralizing antibodies from human serum samples

A newly identified coronavirus, named SARS-CoV-2, emerged in December 2019 in Hubei Province, China, and quickly spread throughout the world; so far, it has caused more than 49.7 million cases of disease and 1,2 million deaths. The diagnosis of SARS-CoV-2 infection is currently based on the detection of viral RNA in nasopharyngeal swabs by means of molecular-based assays, such as real-time RT-PCR. Furthermore, serological assays detecting different classes of antibodies constitute an excellent surveillance strategy for gathering information on the humoral immune response to infection and the spread of the virus through the population. In addition, it can contribute to evaluate the immunogenicity of novel future vaccines and medicines for the treatment and prevention of COVID-19 disease.The aim of this study was to determine SARS-CoV-2-specific antibodies in human serum samples by means of different commercial and in-house ELISA kits, in order to evaluate and compare their results first with one another and then with those yielded by functional assays using wild-type virus. It is important to identify the level of SARS-CoV-2-specific IgM, IgG and IgA antibodies in order to predict human population immunity, possible cross-reactivity with other coronaviruses and to identify potentially infectious subjects.In addition, in a small sub-group of samples, a subtyping IgG ELISA has been performed. Our findings showed a notable statistical correlation between the neutralization titers and the IgG, IgM and IgA ELISA responses against the receptor-binding domain of the spike protein. Thus confirming that antibodies against this portion of the virus spike protein are highly neutralizing and that the ELISA Receptor-Binding Domain-based assay can be used as a valid surrogate for the neutralization assay in laboratories that do not have biosecurity level-3 facilities

A cross-sectional study evaluating hospitalization rates for chronic limb-threatening ischemia during the COVID-19 outbreak in Campania, Italy

The expansion of coronavirus disease 2019 (COVID-19) prompted measures of disease containment by the Italian government with a national lockdown on March 9, 2020. The purpose of this study is to evaluate the rate of hospitalization and mode of in-hospital treatment of patients with chronic limb-threatening ischemia (CLTI) before and during lockdown in the Campania region of Italy. The study population includes all patients with CLTI hospitalized in Campania over a 10-week period: 5 weeks before and 5 weeks during lockdown (n = 453). Patients were treated medically and/or underwent urgent revascularization and/or major amputation of the lower extremities. Mean age was 69.2 +/- 10.6 years and 27.6% of the patients were women. During hospitalization, 21.9% of patients were treated medically, 78.1% underwent revascularization, and 17.4% required amputations. In the weeks during the lockdown, a reduced rate of hospitalization for CLTI was observed compared with the weeks before lockdown (25 vs 74/100,000 inhabitants/year; incidence rate ratio: 0.34, 95% CI 0.32-0.37). This effect persisted to the end of the study period. An increased amputation rate in the weeks during lockdown was observed (29.3% vs 13.4%; p < 0.001). This study reports a reduced rate of CLTI-related hospitalization and an increased in-hospital amputation rate during lockdown in Campania. Ensuring appropriate treatment for patients with CLTI should be prioritized, even during disease containment measures due to the COVID-19 pandemic or other similar conditions

How the First Year of the COVID-19 Pandemic Impacted Patients’ Hospital Admission and Care in the Vascular Surgery Divisions of the Southern Regions of the Italian Peninsula

Background: To investigate the effects of the COVID-19 lockdowns on the vasculopathic population. Methods: The Divisions of Vascular Surgery of the southern Italian peninsula joined this multicenter retrospective study. Each received a 13-point questionnaire investigating the hospitalization rate of vascular patients in the first 11 months of the COVID-19 pandemic and in the preceding 11 months. Results: 27 out of 29 Centers were enrolled. April-December 2020 (7092 patients) vs. 2019 (9161 patients): post-EVAR surveillance, hospitalization for Rutherford category 3 peripheral arterial disease, and asymptomatic carotid stenosis revascularization significantly decreased (1484 (16.2%) vs. 1014 (14.3%), p = 0.0009; 1401 (15.29%) vs. 959 (13.52%), p = 0.0006; and 1558 (17.01%) vs. 934 (13.17%), p < 0.0001, respectively), while admissions for revascularization or major amputations for chronic limb-threatening ischemia and urgent revascularization for symptomatic carotid stenosis significantly increased (1204 (16.98%) vs. 1245 (13.59%), p < 0.0001; 355 (5.01%) vs. 358 (3.91%), p = 0.0007; and 153 (2.16%) vs. 140 (1.53%), p = 0.0009, respectively). Conclusions: The suspension of elective procedures during the COVID-19 pandemic caused a significant reduction in post-EVAR surveillance, and in the hospitalization of asymptomatic carotid stenosis revascularization and Rutherford 3 peripheral arterial disease. Consequentially, we observed a significant increase in admissions for urgent revascularization for symptomatic carotid stenosis, as well as for revascularization or major amputations for chronic limb-threatening ischemia

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level